Merge branch 'drop_files' of https://github.com/m-pilia/vv into m-pilia-drop_files

diff --cc vv/vvMainWindow.cxx
Simple merge

diff --cc vv/vvMainWindow.h
index 2be7e7584caaf78ad91daf261642d5b343eb7449,2d6a21dde238ef34ed446114ed907ad503cfc429..07f38e5f9f415613c68410f8eb35445a504203b8
--- 1/vv/vvMainWindow.h
--- 2/vv/vvMainWindow.h
+++ b/vv/vvMainWindow.h
@@@ -21,12 -21,8 +21,13 @@@
  
  #include <iostream>
  #include <vector>
+ #include <QDropEvent>
 +#include "vtkVersion.h"
 +#if (VTK_MAJOR_VERSION == 8 && VTK_MINOR_VERSION >= 1) || VTK_MAJOR_VERSION >= 9
  #include "ui_vvMainWindow.h"
 +#else
 +#include "ui_vvMainWindowVTK7.h"
 +#endif
  #include "vvMainWindowBase.h"
  #include "vvToolManager.h"
  #include "vvImageReader.h"